In the art of mounting work materials (such as plates and brackets) on anchoring surfaces such as walls and ceilings, it is known to use such devices as plastic shields and lead anchors to make screws grip tightly in blind holes in the anchoring surfaces. These devices are first placed into a hole in the anchoring surface, and then a screw is inserted into the shield or anchor forcing the shield or anchor material to expand against the hole and thereby tightening the fit of the screw in the hole. Problems with such devices are that the device often rotates within the hole in the anchoring material as it is tightened so that although the screw may tighten against the shield or anchor, it will not effectively tighten against the wall itself. Furthermore, stresses are often concentrated near the surface of the anchoring material, therefore making possible surface buckling and chipping. Normally one must match the size of the device closely to the size of the hole and screw. Finally, the normal method of using these devices is to put them on the anchoring surface before the work material is mounted thereon because they are normally of larger diameter than the holes in the work material. The work material is initially placed on the surface to determine where holes are to be made in the surface, but then must be removed while the devices are put in place.
It would be desirable to have a device that overcomes these problems and simplifies the mounting of work materials.
Pleister U.S. Pat. No. 1,248,006 describes a bolt anchor which is placed entirely within a hole and rests on one side of the bolt between the wall of the hole and the bolt with a thickened portion of the anchor adjacent to the tip of the bolt. Threads are preformed in the anchor.
Marks U.S. Pat. No. 2,588,860 shows a screw-hole liner of uniform thickness that is semi-cylindrical and is preshaped to the contour of screw threads.
Huber et al. U.S. Pat. No. 484,204 shows a nut lock that has an elastic locking finger that protrudes out of the hole of the nut after insertion of a uniformly sized locking portion into the nut through a groove therein.